Development Of Experimental Instrument For Flicker Noise Analysis And Study Of Molecular Junction Interface Charge Transport Modes

Research in single-molecule scale requires higher demands on the measuring platform,meanwhile the development of precise instrument is the fundamental of single-molecule science.The community of molecular electronics aims to fabricate molecular integrated circuits by wiring single molecules into circuits,and even for logic programming in the future.During the past decades,the community has made great breakthrough in both experimental and theoretical research.The electronic coupling in molecule-electrode interface is one of the most important research field.Moreover,the characteristic of molecular-electrode contact is different from the macro-ohmic contact and the coupling strength closely related to the connection configuration.The different coupling modes of molecule-electrode will affect the coupling strength obviously,which change the charge transport properties of molecular junctions.In order to understand the coupling mode of molecule-electrode interfaces,we developed flicker noise analysis to gather more information about the coupling modes of moleculeelectrode interfaces.Based on the results of flicker noise analysis,we could extract the coupling modes of molecule-electrode interfaces.In this work,I firstly developed a low noise,full sampling range and highly sensitive logarithmic current-voltage convertor for single-molecule electrical measurement.Secondly,I introduced a PID temperature control system and optimized the logarithmic current-voltage convertor with Miller compensation to improve the stability of the entire system.Thirdly,to acquire reliable flicker noise data,I integrated a hovering control system into the home-built STM-BJ system and wrote a MATLAB code for data processing of flicker noise.In order to verify the reliability of the whole system,the flicker noises of two types of molecular junction with special charge transport properties have been measured and analyzed.The main contents and results of this thesis are as follows:1.Collaborated with Dr.Gabor Meszaros,I developed a logarithmic currentvoltage convertor with full range,high accuracy and stability which is able to process current data from femtoamps to miliamps with up to 9 orders of amplitude.2.I constructed a home-built STM-BJ setup for electrical measurement in single-molecule scale with logarithmic current-voltage convertor.I added a hovering control system to the STM-BJ designed by Prof.Jia Shi and wrote a program for flicker noise data processing and analysis using MATLAB.Finally,I completed the platform for flicker noise data collection and analysis.3.Cooperated with Dr.Zhixin Chen,I analyzed the flicker noise of highly twisted and localized single-molecule junctions.We found that different configurations of molecular junctions of molecules with pyridine-based anchoring can be distinguished from flicker noise.What’s more,we proved that the flicker noise could be used to analyze the transport mode of moleculeelectrode interface.4.Cooperated with Dr.Zhixin Chen,I introduced flicker noise analysis on the molecular junctions with destructive quantum interferences that could be tuned by hydrogen bonds and analyzed the trend of normalizing parameters.We proved that the introduction of intramolecular hydrogen bonds to the meta-benzene ring could suppress the destructive quantum interference.